The 3GPP (Third Generation Partnership Project) discusses a standardization of mobile communication schemes. For example, high-speed wireless communication schemes such as LTE (Long Term Evolution) are standardized in 3GPP. In 3GPP release 12, D2D communication is discussed as a new wireless communication scheme. Note that D2D communication is an LTE extended specification and may be referred to as LTE Device-to-Device Proximity Services.
In D2D communication, a terminal device can directly communicate with another terminal device without transferring data via a base station. Thus, D2D communication is expected to provide communications with small delays. In addition, since D2D communication can be performed even in an area where a radio wave from a base station cannot reach (or an area where a base station does not exist), D2D communication may be useful for extending cell coverage. Furthermore, since D2D communication can be performed even when a base station is not working (for example, after an earthquake), D2D communication may be useful for improving user security. Note that a communication link established between terminal devices for D2D communication may be referred to as a D2D link.
D2D communication may be implemented by using a cellular communication system. That is, D2D communication may use resources of the cellular communication system. When a plurality of D2D links are established, the same resource (for example, radio frequency) may be allocated to the plurality of D2D links when there are a large number of D2D links. Accordingly, spectrum efficiency is high and precious resources are efficiently allocated to users in D2D communication.
As described above, the same resource may be allocated to a plurality of D2D links in D2D communication. Thus, when the same resource is allocated to D2D links that are close to each other, interference may occur between the D2D links.
However, since D2D communication is a new scheme, the interference between the D2D links has not been sufficiently considered in 3GPP. That is, a method for suppressing the interference between the D2D links has not been determined. Note that this problem may arise not only in D2D communication described in 3GPP release 12, but also in any wireless communication system that supports direct communication between terminal devices.